Is this what getting old is like?

I used to get tired at night, gradually, like a on fading scale where there was a lot of grey in the middle where I could go either way. Like
"I'm kinda tired but if something was to be going on I'd get up and out"
or "yeah I'm getting sleepy but I will obviously finish the movie"

Not no more. Now it's like a frying pan to my head every night. One second I'm all "what do you mean Will I stay up if we watch a movie?" All offended.
The next second, I'm dead asleep.